console.log('第一堂课学习内容')

//2.let定义的变量不允许重复声明
var c = 5
var c = 8
console.log(c)

// let d = 9
// let d = 10

//3.let声明的变量不具备变量提升
console.log(e)  //undefined
var e = 8

//相当于
var e 
console.log(e)
e = 8

console.log(f)
let f 
f = 10

